Electronic device that controls the vailidity of information based on a selected function unit

ABSTRACT

An electronic equipment for communications with other nodes via a serial bus interface. The electronic equipment has a plurality of functions, and stores a plurality piece of information representative of the plurality of functions. The communication system selectively reads the stored information and realizes the function corresponding to the read information. Accordingly, communications suitable for each function can be executed via the serial bus interface. An interface control device used with an electronic equipment having a plurality of functions stores a plurality piece of information representative of the plurality of functions. The communication system selectively reads the stored information and realizes the function corresponding to the read information. Accordingly, the electronic equipment can perform communications suitable for each function.

This application is a division of application Ser. No. 09/614,547, filedJul. 12, 2000, now U.S. Pat. No. 6,353,868, which is a division ofapplication Ser. No. 09/414,319, filed Oct. 7, 1999, now U.S. Pat. No.6,138,196, which is a division of application Ser. No. 08/917,295, filedAug. 25, 1997, now U.S. Pat. No. 5,991,842.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an interface control device, anelectronic equipment, and a communication system, and more particularlyto a communication system for digital data transfer using a serial businterface, an electronic equipment for digital data transfer using sucha system, and a control device for controlling such a system.

2. Related Background Art

With the development of recent multimedia techniques, various types ofdata in various formats can be transferred via one digital I/F(interface) system under various communication protocols.

There is an equipment capable of using only one communication protocolalthough it has a plurality of functional units, in which each unit canbe externally controlled and can transfer data to and from externaldevices. One of digital I/F bus systems of this kind is an IEEE 1394serial bus.

In order to deal with nodes having various functions, the IEEE 1394serial bus is generally provided with, in addition to a protocol commonto IEEE 1394, other different communication protocols. In thisspecification, a common protocol independent from functional units ofeach equipment, although it is specific to each serial bus such as IEEE1394 serial bus, is called a fundamental protocol, whereas a protocoldependent upon each functional unit is called a subsidiary communicationprotocol.

Specifically, even for digital data communications in conformity withthe fundamental protocol of a digital I/F bus system, it is generallynecessary that a subsidiary communication protocol defined for each nodeterminal (I/F terminal) matches the protocol of the communicationpartner, and the communication partner is required to have means forconverting the format of received data into a format usable at thecommunication partner.

The subsidiary communication protocol is generally standardized inaccordance with the genre (category) of each equipment or its unit.Therefore, each node has been generally configured as an equipmentcompatible with a single subsidiary communication protocol.

Definition (definition of node information) of an equipment as viewedfrom a digital I/F bus has been difficult to generate if a plurality offunctions provided by the equipment cannot be operated at the same time,or if the unit configuration or the subsidiary communication protocolchanges because of connecting a new unit or attachment.

Even if an equipment is an image input equipment having only a singlefunction, the input image may be used in a different manner at thecommunication partner. In such a case, it is desired that subsidiarycommunication protocols different for each use type such as displaying,recording and printing are separately prepared. It is also necessary toconsider that a different subsidiary communication protocol may be usedby each manufacture of the equipment, even if both the function and usetype are the same.

SUMMARY OF THE INVENTION

The invention has been made under the above circumstances, and aims atconfiguring a communication system while considering a node havingvarious functions and various use types of a digital interface.

It is another object of the present invention to provide an electronicequipment and interface control device capable of communications withvarious nodes via various interfaces.

In order to achieve the above objects of the invention, an electronicequipment of one embodiment has a plurality of functions and stores aplurality piece of information representative of a plurality offunctions. The communication system selectively reads the storedinformation and realizes the function corresponding to the readinformation. Accordingly, communications suitable for each function canbe executed via the digital serial bus interface.

According to another embodiment of the invention, an interface controldevice used with an electronic equipment having a plurality of functionsstores a plurality piece of information representative of the pluralityof functions. The communication system selectively reads the storedinformation and realizes the function corresponding to the readinformation. Accordingly, the electronic equipment can performcommunications suitable for each function.

An electronic equipment or interface control device according to anotherembodiment of the invention, selectively reads information from anotherequipment which stores information on a plurality of functions orinformation on a plurality of subsidiary communication protocols.Therefore, the communication system can perform communications mostsuitable for each function.

A communication system of the invention stores a plurality ofinformation representative of a plurality of functions provided by eachelectronic equipment, and selectively reads the information so that thefunction corresponding to the read information can be realized at theelectronic equipment and optimum communications can be performed.

The other objects and features of the invention will become apparentfrom the following detailed description of embodiments when read inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an example of a communication systemconfigured by using a serial bus of IEEE 1394.

FIG. 2 is a diagram showing the layer structure of a serial bus of IEEE1394.

FIG. 3 is a diagram illustrating an address space allocation of a serialbus of IEEE 1394.

FIG. 4 is a diagram showing the contents of a configuration ROM,addresses being allocated in the manner illustrated in FIG. 3.

FIG. 5 is a diagram showing the configuration of a communication systemaccording to an embodiment of the invention.

FIG. 6 is a diagram illustrating communication cycles of the systemshown in FIG. 5.

FIG. 7 is a diagram showing the detailed structures of a camera/recorderin the system shown in FIG. 5.

FIG. 8 is a diagram illustrating node information stored in aconfiguration ROM provided in the equipment shown in FIG. 7.

FIG. 9 is a diagram showing a data arrangement in a packet to betransmitted under each subsidiary communication protocol of theequipment shown in FIG. 7.

FIGS. 10A and 10B are diagrams showing the details of the dataarrangement shown in FIG. 9.

FIG. 11 is a flow chart illustrating the operation of selecting afunction and a subsidiary communication protocol to be executed by thesystem shown in FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention will be described by using only its preferred embodimentsand with reference to the accompanying drawings.

First, a system on which the embodiments are based will be described,this system being a communication system between a plurality ofelectronic equipments interconnected by serial busses of IEEE-1394-1995(hereinafter simply called 1394 serial busses).

Communication systems using 1394 serial busses have been proposed ascommunication systems for multiplex transfer of digital data and controldata via digital busses to and from various types of digital equipmentssuch as digital video tape recorders (hereinafter called VTRs) anddigital television receivers (hereinafter called TVs).

The 1394 serial bus will be briefly described.

FIG. 1 shows an example of a network system configured by using 1394serial busses. This system has equipments A, B, C, D, E, F, G and H andtwist pair cables of 1394 serial busses interconnecting A and B, A andC, B and B, D and E, C and F, C and G, and C and H. These equipments Ato H may be PCs, digital VTRs, DVDs, digital cameras, hard disks,printers, monitors, and the like.

Interconnection between these equipments can use both a daisy chainscheme and a node branch scheme at the same time, and provides a highdegree of connection freedom.

Each equipment has a unique ID so that all the equipments interconnectedby 1394 serial busses in one network can be identified. The digitalequipments are sequentially connected by a single 1394 serial bus cable,and each equipment provides a repeater function to form one network. APlug & Play function, which is characteristic of the 1394 serial bus,allows automatic recognition of an equipment and its connection statewhen it is connected by a cable to the network.

Also in the system shown in FIG. 1, when an equipment is disconnectedfrom the network or a new equipment is added thereto, automatic busresetting is performed to reset the network configuration andreconfigure a new network. With this function, it is possible to alwaysset and recognize the network configuration at any given time.

The data transfer rates of 100/200/400 Mbps are available, and anequipment having a higher transfer rate supports a lower transfer ratefor data transfer compatibility.

The data transfer mode includes an asynchronous transfer mode and anisochronous transfer mode. In the asynchronous transfer mode,asynchronous data (hereinafter described as Async data) such as controlsignals is transferred, whereas in the isochronous transfer mode,isochronous data (hereinafter described as Iso data) such as real timevideo data and audio data is transferred. These Async data and Iso dataare transferred in a mixed state in each cycle (generally one cycle is125 μs) after a cycle start packet (CSP) indicating a cycle start istransmitted, while giving the Iso data a priority over the Async data.

FIG. 2 is a schematic diagram showing the functional structure of the1394 serial bus.

As shown in FIG. 2, the 1394 serial bus is configured as a layer(hierarchical) structure. The constituent at the lowest physical levelis a 1394 serial bus cable whose connector is connected to a connectorport. At the level higher than this connector port, a physical layer anda link layer are provided as hardware.

This hardware portion is substantially an interface chip. The physicallayer of the hardware portion is used for coding, connector control andthe like, and the link layer is used for packet transfer, cycle timecontrol and the like.

A transaction layer as firmware is used for the management of transferdata (transaction), and issues commands such as data read and write. Aserial bus management manages the connection state and ID of eachconnected equipment for the node control and network configurationmanagement.

The functions of a bus manager and an isosynchronous resource managerare included in this serial bus management. These hardware and firmwareare the fundamental constituents of the 1394 serial bus. Namely, thefundamental protocol of the 1394 serial bus described previously isconfigured by the firmware up to this transaction layer.

On the other hand, an application layer in a software portion is made ofsoftware defined by the above-described subsidiary communicationprotocols, and changes with each software. Namely, this applicationlayer defines what type of data is transmitted over the 1394 serial bus.

Next, with reference to FIG. 3, addressing of the 1394 serial bus willbe described. As shown, an address space of a 64-bit width in conformitywith IEEE 1212 regulations is defined for the 1394 serial bus. The first10 bits of the 64-bit address are called a bus ID which is used for thediscrimination between busses. The next 6 bits are called a node IDwhich is used for the discrimination between equipments. The remaining48 bits are used as an address space which can be used solely by eachequipment.

The 48-bit address space is further divided into a 20-bit field and a28-bit field. An area represented by “FFFFF” of the first 20 bits is aregister space which is used for information exchange betweenequipments.

The first 512 bytes of the register space include a kernel of a knownCSR architecture, and the next 512 bytes are used as a serial busregister. The specific contents of these areas are well known and thedetailed description thereof is omitted. These areas and the next1024-byte configuration ROM and a portion of a unit space areimplemented on each equipment.

The configuration ROM is structured, for example, as shown in FIG. 4 inorder to describe the functions of each node. An offset address shown inFIG. 4 indicates a relative address from “FFFFF0000000”, and theconfiguration ROM is located from “FFFFF0000400”.

A bus information block (indicated in FIG. 4 by Bus_info_block) storesdata such as an ID of an equipment supply company. A root directory(indicated in FIG. 4 by Root_directory) stores information specific toeach node and a storage location of the next unit directory (indicatedin FIG. 4 by Unit Directory). The unit directory hierarchically storesdata representative of the functions of each equipment, datarepresentative of usable subsidiary communication protocols, and otherdata.

An example of a communication system according to the present inventionwill be described.

FIG. 5 shows an example of a communication system according to thepresent invention.

The system shown in FIG. 5 is provided with digital equipmentsincluding: a PC (personal computers), a TV, a VTR, and a camera/recorder(hereinafter called a CAM) having a function of picking up a movingimage and a still image. 1394 serial buses connect CAM and TV, TV andPC, and PC and VTR. Each of these digital equipments has a function ofrepeating digital data and control data on the 1394 serial bus.

A cable of a 1394 serial bus is constituted of three sets of shieldedpaired wires. Paired wires of each set-are used for transfer of protocolsignals and data and for supply of electric power. Even if the systemhas an equipment whose power source is turned off, the operation of thewhole system is ensured.

The fundamental structure of each digital equipment, for example, VTR isconstituted of: a deck unit; a tuner unit; an operation unit used asuser interface; a display unit; a microcomputer for the control of thewhole operation, for the generation of communication packets, for thestorage of addresses, and the like; a digital interface (digital I/F)unit of 1394 serial buses; and a switch unit for switching between thedeck unit, tuner unit, and digital I/F unit. The fundamental structureof TV is constituted of a monitor unit and an amplifier unit in place ofthe display unit and deck unit of VTR. The fundamental structure of CAMis constituted of a camera unit in place of the tuner unit. Thefundamental structure of PC is constituted of a CPU, an operation unit,and an image processing unit, and similar to other digital equipments,of a switch unit and a digital I/F unit.

Communications are performed by using 1394 serial buses at apredetermined communication cycle (125 μs) as illustrated in FIG. 6.Time sequential data such as video data and audio data is transmittedthrough isochronous communication which ensures a transmission bandwidthat a predetermined data rate, and control data such as control commandsis transmitted through asynchronous communication when it becomesnecessary.

In such communications, at the start of each communication, a cyclestart packet is transmitted, and thereafter packets are transmitted fora predetermined period for isochronous communication.

Packets for isochronous communication are assigned specific channelnumbers so that isochronous communication for a plurality of channelscan be performed at the same time. For example, assuming thatcommunication from CAM to VTR is assigned a channel number “1”, CAMtransmits isochronous communication packets of the channel number “1”immediately after the cycle start packet is transmitted. VTR monitorspackets on the bus and picks up packets having the channel number “1” sothat isochronous communication between CAM and VTR can be realized.

Similarly, assuming that communication from TV to PC is assigned achannel number “2”, each packet of the channel number “2” is transmittedover the bus after each packet of the channel number “1” so thatisochronous communication for the channels “1” and “2” can be executedin parallel.

After all isochronous communication packets are transmitted in eachcommunication cycle, the following period until the next cycle startpacket is received, is used for asynchronous communication.

Next, bus management allowing the bus system operation will bedescribed.

An equipment operating as a bus manager first retrieves the informationon the network configuration and the connection state of all nodes, andgives the definition of each node ID and controls isochronouscommunication.

In the communication system described above, when a power is turned on,a new digital equipment is connected, or any equipment is disconnected,topology is automatically set by assigning each equipment (node) a nodeID (physical address such as #0, #1, #2 and #3 shown in FIG. 5) inaccordance with the new interconnection state, as in the followingprocedure which uses an addressing program and an address table storedin the memory of the microcomputer.

The node ID assigning procedure will be briefly described. Thisprocedure is composed of determination of a system hierarchicalstructure and assignment of a physical address of each node.

In this example, for the digital equipments described above, it isassumed that TV is a node A, CAM is a node B, PC is a node C, and VTR isa node D.

Each node notifies a partner node connected by the 1394 serial bus thatthe partner is a parent. In this case, the first notice has a priority.The parent/child relationship of this system is finally determined,namely, the hierarchical structure of the system and a root node whichis not a child of any node are determined.

Specifically, in the example shown in FIG. 5, the node D notifies thenode C that the node C is a parent, and the node B notifies the node Athat the node B is a parent. If the node A notifies the node C that thenode C is a parent and the node C notifies the node A that the node A isa parent, the first notice has a priority and if the notice by the nodeC is faster, the node A is a parent of the node C. In this case, thenode A is not a child of any other node and becomes a root node.

After the parent/child relationship of the digital equipments isdetermined in the above manner, physical addresses are assigned. Thebasics of physical address assignment are that a parent node gives achild node an address assignment permission and that each child nodestarting from the node connected to a younger port number is given anaddress assignment permission.

In the parent/child relationship determined as in the case of FIG. 5,the node A first gives the node B an address assignment permission.Therefore, the node B gives itself a physical address #0. This isnotified to the bus to broadcast the effect “physical address #0 alreadyassigned” to all other nodes.

Next, the node A gives the node C an address assignment permission, andthen the node D which is a child of the node C is given an addressassignment permission. Therefore, the node D gives itself a physicaladdress #1 next to the physical address #0, and notifies this effect tothe bus.

Thereafter, the node C assigns itself a physical address #2 and notifiesthis effect to the bus. Lastly, the node A assigns itself a physicaladdress #3 and notifies this effect to the bus.

Next, the data transfer procedure will be described.

Data transfer becomes possible after the physical addresses areassigned. In the case of 1394 serial buses, however, prior to the datatransfer, the root node arbitrates bus use privileges.

If a node wishes to start data transfer, it requests a bus use privilegeto the parent node. The root node arbitrates requests for bus useprivileges from respective nodes. Prior to data transfer, a node gainedthe bus use privilege designates a transfer rate and notifies one of100, 200 and 400 Mbps to a transmission destination node.

Thereafter, in the case of isochronous communication, the transmissionoriginating node starts data transfer at the designated channelimmediately after it receives the cycle start packet transmittedsynchronously with the communication cycle from the root node operatingas a cycle master. The cycle master adjusts the time at each node aswell as the transmission of the cycle start packet to the bus.

In the case of asynchronous communication for the transfer of controldata such as commands, after the end of isochronous communication ineach communication cycle, arbitration for asynchronous communication isperformed and then data transfer starts from the transmissionoriginating node to the transmission destination node.

FIG. 7 is a system block diagram showing the detailed structure of thecamera/recorder (CAM) shown in FIG. 5 as one example of the digitalequipment of this invention.

In FIG. 7, reference numeral 1 represents an is image pickup unitconstituted of a lens, a CCD, fundamental image pickup circuits, and thelike. The image pickup unit 1 picks up a subject image and executescamera signal processing such as adjustments of luminance and color of apicked-up image. Image data processed by the image pickup unit 1 isoutput in the format suitable for a video processing unit 2 and adigital camera processing unit 3.

The video processing unit 2 digitizes image data supplied from the imagepickup unit 1 and executes a coding process for the compression of imagedata in accordance with a predetermined algorithm such as a DVC formatcompression scheme and a MPEG scheme. The video processing unit 2 alsoperforms the conversion of image data format suitable for transmission.

The digital camera processing unit 3 digitizes image data supplied fromthe image pickup unit 1, performs image processing such as adjustmentsof an image size and sampling, and executes a coding process for thecompression of image data in accordance with a JPEG scheme or the like.The digital camera processing unit 3 also performs the conversion ofimage data format suitable for transmission.

Reference numeral 4 represents a switch circuit for selecting either amoving image signal sig1 from the video processing unit 2 or a stillimage signal sig2 from the camera processing unit 3 and supplies it viaanother switch circuit 22 to a 1394 serial bus I/F circuit 5. This 1394serial bus I/F circuit 5 includes a reset circuit 19 for a 1394 serialbus 13.

Image data supplied from the video processing unit 2 or digital cameraprocessing unit 3 can be recorded or reproduced by arecording/reproducing unit 20 without being transmitted via the 1394bus. The reproduced data may be transmitted via the 1394 bus. Therecording/reproducing unit 20 includes recording media and othernecessary equipments for recording/reproducing operations.

Reference numeral 6 represents a system control circuit (controller)which is constituted of a microcomputer, a memory and the like. Thecontroller 6 has an I/F control and address conversion circuit 7 whichtransfers, between the controller 6 and 1394 I/F circuit 5, nodeinformation and command/status information contained in the datatransmitted from the 1394 I/F circuit to the 1394 bus 13.

Reference numeral 8 represents a first configuration ROM (CR1) whichconstitutes the already-described configuration ROM. This firstconfiguration ROM stores node information for a first protocol which isused for the transmission via the 1394 bus 13 of the moving image signalsig1 and its associated command/status information, the moving imagesignal being obtained by a digital moving image camera/recorder (firstunit) realized by a combination of the image pickup unit 1 and videoprocessing unit 2. Proper node information in this operation state ofthe equipment is stored in advance in the first configuration ROM 8during the manufacture.

Reference numeral 9 represents a second configuration ROM (CR2). Thissecond configuration ROM stores node information for a second protocolwhich is used for the transmission via the 1394 bus 13 of the stillimage signal sig2 and its associated command/status information, thestill image signal being obtained by a digital still imagecamera/recorder (second unit) realized by a combination of the imagepickup unit 1 and camera processing unit 3. Proper node information inthis operation state of the equipment is stored in advance in the secondconfiguration ROM 9 during the manufacture.

Reference numeral 10 represents a command/status register (C & Sregister) used by both the first and second units and storing unitcontrol information. Reference numeral 11 represents a control unit forcontrolling the operations of the first and second units in accordancewith commands loaded in the C & S register 10 and also for controllingsubsidiary communication protocols.

The 1394 serial bus I/F circuit 5 and controller 6 constitute theinterface control device of this embodiment.

Reference numeral 12 represents a video/camera switch which selects theoperation of the electronic equipment of this embodiment as viewed fromthe 1394 bus 13, either as the digital moving image camera/recorder(first unit) or digital still image camera/recorder (second unit).

Reference numeral 14 represents a control signal and its command/statussignal for the 1394 I/F circuit 5, reference numeral 15 represents acontrol signal for the switch circuit 4, reference numeral 16 representsa control signal for the video processing unit 2, reference numeral 17represents a control signal for the camera processing unit 3, referencenumeral 18 represents a control signal for the image pickup unit 1, andreference numeral 21 represents a control signal for therecording/reproducing unit 20.

FIG. 8 is a diagram showing node information of CAM as viewed from the1394 bus 13, the node information being mapped in the configuration ROMand the unit controlling command/status register. As shown, in thisembodiment, the configuration ROM is constituted of the first and secondconfiguration ROMs 8 and 9 (CR1, CR2).

Specifically, in this embodiment, in accordance with the status of theelectronic equipment (whether it is used as the digital moving imagecamera/recorder or the digital still image camera/recorder), one of thefirst and second configuration ROMs 8 and 9 can be selected from thebus. Irrespective of which one of the configuration ROMs 8 and 9 isused, the C & S register 10 is used as the common area RAM.

FIG. 9 shows the contents of data to be transmitted by a subsidiarycommunication protocol of the digital moving image camera/recorder(first unit) or digital still image camera/recorder (second unit), thedata being arranged in a data packet transmitted by the 1394 fundamentalcommunication protocol. Each packet is added with a packet headercorresponding to the fundamental communication protocol of a 1394 serialbus, and data corresponding to each subsidiary communication protocol isadded to a payload area.

With reference to FIGS. 7 to 9, an operation of the digital equipment asone example of this embodiment which changes from the digital movingimage camera/recorder to the digital still image camera/recorder will bedescribed.

It is assumed that the electronic equipment of this embodiment havingthe structure shown in FIG. 7 operates as the digital moving imagecamera/recorder and communicates with another node by supplying nodeinformation onto the 1394 bus 13 via the 1394 serial bus I/F circuit 5,under the first subsidiary communication protocol stored in the firstconfiguration ROM (CR1) 8.

In this case, the compressed moving image signal sig1 obtained by thevideo processing unit 2 is the data in conformity with the SD format ofthe DVC format, i.e., the variable length coded data after discretecosine transformed, and is a signal having the format corresponding tothe video track with sub-code data and AUX data. Such a moving imagesignal sig1 is transmitted via the switch circuit 4 and 1394 I/F circuit5 in the isochronous communication mode.

At the same time, in the asynchronous communication mode, command andstatus information for the control of the digital moving imagecamera/recorder is transmitted. A reception command is stored in the C &S register 10. In accordance with the stored reception command, thecontrol unit 11 controls the video processing unit 2 by using thecontrol signal 16.

In this state, the digital still image camera/recorder (second unit) istransparent from the 1394 serial bus 13. In this case, for example, the1394 serial bus I/F circuit 5 can be used as a dubbing terminal ofcommunication to another digital moving image camera/recorder. Asubsidiary communication protocol used in this case is an IEEE 1394 AV/Cprotocol.

In contrast with the above, if a user uses the electronic equipment ofthis embodiment as the digital still image camera/recorder, it is may beused, for example, as a digital still image pickup equipmnt for anunrepresented personal computer. In this case, a protocol for thecommunication with this personal computer is a still image subsidiarycommunication protocol different from the AV/C protocol.

The outlines of an AV/C protocol and a digital still image protocol willbe described. FIG. 10A shows the structure of an isochronous packet usedby the AV/C protocol, and FIG. 10B shows the structure of an isochronouspacket used by the digital still image protocol.

The AV/C protocol is a well known subsidiary communication protocol, anddefines a real time data transfer protocol using 1394 isochronous datatransfer and an isochronous data flow control. For the real timetransfer, the AV/C protocol defines a CIP (Common Isochronous Packet).As shown in FIG. 10A, a CIP and real time (AV) data are stored in thedata field of the isochronous packet.

The length of a source packet of the AV/C protocol is a fixed lengthspecific to each equipment. The source packet is divided into one, two,four, or eight data blocks which are sequentially transmitted as aplurality of isochronous packets. The reception side uses a time stampfield in CIP for recovering real time data of the original packet fromthe divided isochronous packets.

While the equipment is under operation, an empty packet only with apacket header and a CIP header is transmitted even if there is no datato be transmitted.

The AV/C protocol prepares a FCP (Function Control Protocol) in order tocontrol equipments on the 1394 serial buses. This FCP packet frame istransmitted by using an asynchronous packet for the control oftransmission/reception of the control command.

As shown in FIG. 10B, the isochronous packet structure of the stillimage protocol is made to have a normal structure without a CIP and thelike in the data field as in the case of the AV/C protocol. This datafield stores data in the color signal format discriminated by thefollowing modes.

Mode 0: YUV (4: 4: 4) format

Mode 1, Mode 3: YUV (4: 2: 2) format

Mode 2: YUV (4: 1: 1) format

Mode 4: RGB format

Mode 5: Y (Mono) format

Eight-bit pixel data is stored for each of Y, U, V, R, G and B of theabove format.

The still image protocol is structured to perform only data write fromthe transaction layer, without having FCP as in the case of the AV/Cprotocol.

The description will be given for the operation after the electronicequipment of this embodiment is switched from the digital moving imagecamera/recorder to the digital still image camera/recorder by activatingthe video/camera switch 12.

Upon detection of an activation of the video/camera switch 12, thecontroller 6 temporarily stops the bus control of the 1394 I/F circuit 5in order to execute the resetting of the 1394 serial bus 13 and thereconfiguration of the bus management configuration.

The digital still image camera/recorder (second unit) is reconfiguredand the C & S register 10 is set use with the digital still imagecamera/recorder. Next, in order to change the node information of the1394 serial bus I/F circuit 5 from the first configuration ROM 8 to thesecond configuration ROM 9, the address setting of the I/F control andaddress conversion circuit 7 is changed. Namely, since the configurationROMs 8 and 9 are located at different addresses in the above-describedaddress space, the address setting is changed to select the secondconfiguration ROM 9.

Thereafter, in order to reconfigure the management configuration of the1394 serial bus 13 under the reset state, the bus interconnection of the1394 serial bus I/F circuit 5 is recovered. In this manner, theelectronic equipment of this embodiment is newly defined as the digitalstill image camera/recorder having the still image subsidiarycommunication protocol, in accordance with the new bus managementconfiguration and the node information in the second configuration ROM9. This new definition is detected by the root node which controls thebus management of the system shown in FIG. 5, and therefore recognizedby the system.

In operation of the electronic equipment of this embodiment as thedigital still image camera/recorder, a partner node is generally andpresumably a personal computer (PC). In such a case, an image signalpicked up with the image pickup unit 1 is converted by the cameraprocessing unit 3 into image data matching the format requested by PC.This image data is supplied as a baseband image signal sig2 to PC viathe switch circuit 4, 1394 serial bus I/F circuit 5, and 1394 bus 13. Inthis case, the above-described still image subsidiary communicationprotocol is used.

At the same time, PC sends a command which is stored in the C & Sregister 10 to set the equipment as the digital still imagecamera/recorder. During this time, the digital moving imagecamera/recorder (first unit) is transparent from the 1394 serial bus 13.

FIG. 11 is a flow chart illustrating the switching operation between thedigital video (moving image) equipment and the digital camera (stillimage) equipment of the embodiment described above. The controller 6 hasbuilt-in software of this flow chart and the subsidiary communicationprotocols used for the communication by the first and second units.

Referring to FIG. 11, at Step S1 the controller 6 checks whether thereis a change in the device mode, i.e., whether the video/camera switch 12is activated. If a mode change is detected, the flow advances to Step S2whereat the resetting operation of the 1394 serial bus 13 starts and thebus control by the 1394 serial bus I/F circuit 5 is temporarily stopped.

At Step S3 it is checked whether the digital equipment of thisembodiment has been changed to the digital moving image camera/recorder(first unit) or to the digital still image camera/recorder (second unit)by the video/camera switch 12.

If changed to the digital video (moving image camera/recorder), the flowadvances to Step S4 to perform the unit control corresponding to thesystem configuration of the digital video, at Step S5 the C & S register10 is set for use with the digital video, and at Step S6 the addresssetting of the I/F control and address conversion circuit 7 is changedin order to set the node information of the 1394 serial bus I/F circuit5 to have the information stored in the first configuration ROM 8.

If it is judged at Step S3 that the equipment has been changed to thedigital camera (still image camera/recorder), the flow advances to StepS7 to perform the unit control corresponding to the system configurationof the digital camera, at Step S8 the C & S register 10 is set for usewith the digital camera, and at Step S9 the address setting of the I/Fcontrol and address conversion circuit 7 is changed in order to set thenode information of the 1394 serial bus I/F circuit 5 to have theinformation stored in the second configuration ROM 9.

After the processes at Steps S4 to S6 or Steps S7 to S9, the reset stateof the 1394 serial bus 13 started at Step S2 is released to recover thebus connection of the 1394 serial bus I/F circuit 5. At Step S11 theroot node executes a new bus management process after the system changeand recognizes the equipment of this embodiment either as the movingimage camera/recorder having the AV/C protocol or as the still imagecamera/recorder having the still image subsidiary communicationprotocol, in accordance with the contents of the configuration ROM 8 or9.

As described so far in detail, according to the embodiment, differentsubsidiary communication protocols are selectively used to perform datacommunication via the 1394 serial bus I/F circuit 5. In this case, theequipment (having the structure such as shown in FIG. 5) having aplurality of units unable to operate at the same time is not required tohave the C & S register independently for each unit. Even if the nodeinformation is required to be changed upon connection of a newequipment, the management configuration of the 1394 serial bus 13 can bereconfigured automatically.

As described above, the electronic equipment of this embodiment hasconfiguration ROMs which store information on a plurality of functionalunits and a plurality of subsidiary communication protocols, and thesystem can selectively use one of a plurality of subsidiarycommunication protocols and one of a plurality of functional units.

Many widely different embodiments of the present invention may beconstructed without departing from the spirit and scope of the presentinvention. It should be understood that the present invention is notlimited to the specific embodiments described in the specification,except as defined in the appended claims.

What is claimed is:
 1. An electronic device including a first functionunit, a second function unit and a digital interface, comprising: aselector which selects the first function unit and the second functionunit; a first memory which stores first information includinginformation about the first function unit; a second memory which storessecond information including information about the second function unit;and a controller which controls the first information so as to be validand the second information so as to be invalid if the first functionunit is selected by the selector.
 2. A device according to claim 1,wherein the controller controls the second information so as to be validand the first information so as to be invalid if the second functionunit is selected by the selector.
 3. A device according to claim 1,wherein the first information includes information about aconmmunication protocol of the first function unit, and wherein thesecond information includes information about a communication protocolof the second function unit.
 4. A device according to claim 1, whereinthe controller resets the digital interface in accordance with anoperation of the selector.
 5. A device according to claim 1, wherein thefirst function unit has a function for sensing and recording a movingimage, and wherein the second function unit has a function for sensingand recording a still image.
 6. A device according to claim 1, whereinthe first function unit has a function for sending a moving image, andwherein the second function unit has a function for sending a stillimage.
 7. A device according to claim 1, wherein the digital interfaceis connectable to a serial bus.
 8. A device according to claim 7,wherein the digital interface conforms to IEEE 1394 standard.
 9. Adevice according to claim 1, wherein the electronic device is a digitalcamera.